1. Field of the Invention
The present invention relates to a laminated type inductor, more particularly, to a laminated type inductor used as a noise filter, and other suitable devices.
2. Description of the Related Art
Generally, when a laminated type inductor is used as a noise filter for a high-frequency signal line, low permeability material is used for a magnetic-substance layer. However, the laminated type inductor made of low permeability material has a problem in that it is easy to generate a link in the waveform of the high-frequency signal.
As a countermeasure, a conventional laminated type inductor 1 is shown in FIG. 5. The laminated type inductor 1 is constructed such that a high permeability coil section 2 including magnetic-substance layers made of high permeability materials, and a low permeability coil section 3 including magnetic-substance layers made of low permeability materials are laminated and integrally fired. Coil conductors 4-6 in the high permeability coil section 2 and coil conductors 7-9 in the low permeability coil section 3 are electrically connected in series through via holes (not illustrated) to define a spiral coil L. One end (coil conductor 9) of the spiral coil L is connected to an external electrode 11. The other end (coil conductor 4) thereof is connected to an external electrode 12.
Moreover, a laminated type inductor 21 is also shown in FIG. 6. A laminated type inductor 21 is constructed such that a high permeability coil section 22 including magnetic-substance layers made of high permeability materials, a low permeability coil section 23 including magnetic-substance layers made of low permeability materials, and an intermediate section 24 made of a non-magnetic material which is disposed between the coil sections 23 and 24 are laminated and integrally fired. Coil conductors 25-28 arranged in the high permeability coil section 22 and coil conductors 29-32 arranged in the low permeability coil section 23 are electrically connected in series through via holes (not illustrated) to define a spiral coil L.
In the conventional laminated type inductors 1 and 21, when the magnetic field H1 generated in the high permeability coil sections 2 and 22 and the magnetic field H2 generated in the low permeability coil sections 3 and 23 cause mutual interference, the noise suppressing effect is insufficient. To prevent the mutual interference of the magnetic fields H1 and H2, the laminated type inductor 1 shown in FIG. 5 has a large distance D between the coil conductors 4-6 of the high permeability coil section 2, and the coil conductors 7-9 of the low permeability coil section 3. However, as the distance D increases, the size of the laminated type inductor 1 also increases.
On the other hand, in the laminated type inductor 21 shown in FIG. 6 the intermediate section 24 is located between the high permeability coil section 22 and the low permeability coil section 233gv to prevent the mutual interference of magnetic fields H1 and H2. However, it is technically difficult to accomplish integrally baking both the magnetic material for the coil sections 22 and 23, and the dielectric material for the intermediate section 24, because the physical structure and the rate of heat-shrinking of both are substantially different. Thus, controlling the manufacturing processes is complicated.
To overcome the above-described problems, preferred embodiments of the present invention provide a small-sized laminated inductor with a substantially simplified baking process.
According to preferred embodiments of the present invention, a laminated type inductor including a low permeability coil section in which magnetic layers made of a relatively low permeability material and coil conductors are laminated, and a high permeability coil section in which magnetic layers made of a relatively high permeability material and coil conductors are laminated, the low permeability coil section and the high permeability coil section are laminated such that the coil conductors of the low permeability coil section and the coil conductors of the high permeability coil section are electrically connected in series to define a spiral coil, and the winding direction of the coil conductors in the low permeability coil section and the winding direction of the coil conductors in the high permeability coil section are opposite to each other.
When the low permeability coil section and the high permeability coil section are bonded together, since both of them are made of magnetic materials without using a different material, bonding reliability is substantially improved.
Moreover, since the winding direction of the coil conductors in the low permeability coil section and the winding direction of the coil conductors in the high permeability coil section are arranged in the opposite direction, mutual interference of the magnetic field produced in the low permeability coil section and the magnetic field produced in the high permeability coil section is prevented.
Other features, elements, characteristics and advantages of the present invention will become apparent from the following description of preferred embodiments thereof with reference to the attached drawings.